Monopolar tissue cutting devices such as snares are known which employ RF energy, applied between the snare loop and a grounding pad, to provide a cutting arc. The cutting arc passes through the tissue as the snare loop is tightened around the polyp cauterizing the lesion and assisting the snare in excising the polyp. In a monopolar snare, the RF energy typically travels through a significant portion of the polyp from the snare to the ground.
Bipolar snares have also been developed which are formed by two electrode wires electrically insulated from each other. Alternatively, a snare loop may be formed from a first electrode wire while a second electrode wire is exposed at an end of the lumen or sheath. Thus, as the bipolar snare is tightened around the polyp and RF energy is applied across the two electrodes, the polyp is severed from the surrounding tissue.
However, these arrangements have resulted in unwanted heat being generated due to short circuiting or uneven distribution of the area of contact between the electrodes and the surface of the polyps.